METHOD 1: THE IN-GAME WAY
NOTE: If you're new or inexperienced with SRB2, this way is easier.
1) Start SRB2.
2) Click "Options".
3) Click "Server Options".
4) Replace srb2.servegame.org:28900 with the alternative MS address of your choice. For example, if you want to connect to Cue's MS, type in ms.srb2.org:28900.
5) Leave the server options menu.
6) Congrats! You've just changed the master server address!

METHOD 2: THE CONFIG WAY
1) Open your SRB2 Folder.
2) Double-click on "config.cfg".
3) If a prompt appears, tell the computer to open config.cfg using notepad.
4) Scroll down untill you see "masterserver". If you can't find it, go Edit >> Find and type in "masterserver".
5) Replace "srb2.servegame.org:28900" with the alternative master server address. For example, if you want to connect to Cue's MS, type in "ms.srb2.org:28900". Don't remove the quotation marks around the address.
6) Save the file.
7) Run SRB2.
8) Congrats! You've changed the master server address!

This should help you guys for now. You only have to do ONE of the two methods, but it's up to you on which one you'd prefer to do.

CURRENT ALTERNATIVE MASTER SERVER LIST:
None yet! If you are hosting your own master server, PM me and I'll see about putting it on this list.

NOTICE: SigSev's MS is down, the only working Master Server is now Cue's Official Master Server (ms.srb2.org:28900) please use this instead.

Just so you are all aware, there has been a drastic change in the structure of the official Master Servers. There are now TWO official Master Servers: Cue's MS and BlueWarrior's MS.

<strike>
The one that SRB2 connects to by default (srb2.servegame.org) now redirects to BlueWarrior's Official SigSev MS (ms.sigsevcafe.com). This is a Master Server with a different and much smaller set of rules than the old MS had. Those rules can be found here.</strike>

Disregard that, SigSev is down until further notice.

--

There is also Cue's Official Master Server (ms.srb2.org), which is a Master Server with specific rules and guidelines that must be followed when playing. Those rules are the 'old' rules that should be familiar (no roleplaying, no SA City, et cetera). More information can be found here.